PLANT PHYS EXAM 1

what are the unique properties of water

• -high specific heat and thermal conductivity:

  • provides temperature stability.

  • can absorb and redistribute large amount of heat without temperature changes

  • prevents cell overheating

  • allows heat exchange between cell and external environment without variation in internal cell temp

• high heat of fusion:

  • the amount of heat needed to convert from solid to liquid

• high heat of vaporization:

  • energy required to convert liquid water to water vapor

  • accounts for cooling associated with evaporation

adhesion

the attraction between different kinds of molecules

cohesion

strong mutual attraction between water molecules

tension

describe the process of diffusion

the spontaneous movement of substances down a concentration gradient to equilibrium from a region of higher concentration to a region of lower concentration

describe the process of bulk flow

the pressure driven movement of water molecules from one place to another due to differences in potential energy that occurs when external force is applied

describe the process of osmosis

water flows spontaneously from a region of lower solute concentration to a region of higher solute concentration

what is water potential and its component potentials

• water potential is a measurement that predicts which way water will tend to flow between the plant cell and its surroundings or between different parts of a plant

• psi(P)= the pressure potential (the cell wall force)

• psi(S)= the osmotic or solute potential(fluid and solutes inside cell)

• psi(M)= the matrix potential (adhesion of water to solid surfaces; cell wall, soil, seed coat

what role do aquaporins play in the transport of water

• aquaporins form channels that mediate water transport

• provide a more rapid rate of water movement

• greater content of water movement intracellularly

what is the driving force behind transpiration

• a difference in water potential between the substomatal air and the atmosphere

• a difference in vapor pressure between the substomatal air and the atmosphere

how to environmental factors influence the rate of transpiration water loss

• temperature: increased temp leads to a higher rate of transpiration

• humidity: lower humidity increases rate of transpiration

• higher light: increased rate of transpiration

• increased wind speed increases transpiration

describe the anatomy of water-conducting tissues in plants

the xylem forms a continuous system of vessels and tracheids that transport water and dissolved mineral form the roots to the rest of the plant

why is the continuity of a water column essential to water transport and plant water relations

a continuous water column allows the plant to move water from the soil to the leaves against gravity

how is soil water transported into roots

water is transport into the roots through osmosis, where root hair cells transport mineral ions into the roots to lower water potential and increase water intake

what are the properties of soils

• size of soil particles

• density of fixed negative charges

• specific surface area

• ion exchange in the soil

how do the properties of soils dictate the availability of nutrients to plants

properties of soil dictate the plant nutrient availability by influencing the chemical form and solubility of nutrients, the soils capacity to hold and supply nutrients, and the activity of microorganisms that transform them

by what mechanisms are solutes transported across membranes, including the role of membrane transport proteins

• simple diffusion: the spontaneous movement of molecules down a concentration gradient, leading to equilibrium

• facilitated diffusion: the rapid, passive, protein assisted diffusion of solutes across membranes; movement down a concentration gradient mediated by carrier proteins and channel proteins

• active transport: transport across a membrane that moves up the concentration gradient; requires energy, unidirectional, mediated by carrier proteins, and it generates gradients that drive other transport processes

how do solute ions move through root tissues and cell walls

• apoplastic pathway: water and solutes enter through the cell walls and intercellular spaces

• symplastic pathway: ions enter symplast by crossing the plasma membrane through active transport or facilitated diffusion, and then move between cells through the plasmodesmata

how do soil microorganisms assist plants in acquiring nutrients for uptake

• endomycorrhiza: fungi penetrates plant roots and produce arbuscules, which press up against the cell membrane and exchange nutrients

• ectomycorrhia: form a sheath surrounding the root to form a Hartig net in the apoplastic space of the root cortex, which increases the absorption of minerals

what are the methods to study plant mineral nutrition

• hydroponic solutions used to simulate the nutrient environment; much simpler than soil

  • provides nutrients in higher concentrations that that of typical soil

• nutrient film: roots are exposed to a shallow stream of continuously flowing nutrient rich soil

what is the distinction between essential and beneficial nutrients in plants

• essential nutrients are required for a plant to complete a life cycle, part of some essential plant constituent or metabolite, and are involved in an essential biological process

• beneficial nutrients may not be universally required by plant but may promote plant growth and development if present

what is the distinction between macronutrients and micronutrients in plants

• macronutrients are used for producing the plant body and for carrying out essential physiological processes

• micronutrients are recycled by the plant and carry out catalytic and regulatory roles

what symptoms are associated with nutrient deficiency

• chlorosis, the loss of chlorophyll pigment

• necrosis, the death of cells and tissues